1. Field
The described technology relates generally to an inspection system using a scanning electron microscope.
2. Description of the Related Art
In general, flat panel displays such as a liquid crystal display (LCD) and an organic light emitting diode (OLED) display are formed by depositing a plurality of thin films and wires. To inspect for existence of impurities or particles on the thin film of the flat panel display, or a short circuit of the wires, an inspection system using an automatic optical inspection (AOI) unit or a vacuum scanning electron microscope (SEM) is used.
The automated optical inspection photographs an inspection object by using an optical system to determine defect existence of the inspection object. However, the automated optical inspection only determines the defect existence of the inspection object, and cannot confirm a cause of the defect such that the cause of the defect must be analyzed by the vacuum scanning electron microscope.
The vacuum scanning electron microscope (SEM) is limited to a size of the inspection object to be observed by a size limitation of a vacuum chamber. A vacuum scanning electron microscope that is capable of observing a semiconductor wafer of up to 30 inches has been developed, however usage of the vacuum scanning electron microscope is difficult for a flat panel display of a size from 730×920 mm to 2200×2500 mm because of the size limitation of the vacuum chamber such that the inspection object is analyzed after cutting it.
In a case of increasing the size of the vacuum chamber to be applied to the flat panel display, secondary electrons (SE) or back-scattered electrons (BSE) from an inspection object positioned in the vacuum chamber cause interference by a charging effect generated in the vacuum chamber such that image observation of the inspection object is difficult, and carbon contamination by a hydrocarbon compound (HxCx) may be generated due to a pump used for the vacuum chamber.
Also, after confirming defect existence of the inspection object by using the automated optical inspection, the inspection object is moved to the vacuum scanning electron microscope to analyze the defect cause such that the inspection process is complicated, and the inspection object must be cut before using the vacuum scanning electron microscope such that the inspection process is more complicated, and furthermore, the automated optical inspection and the vacuum scanning electron microscope must be separately installed such that a space occupied by the inspection system is increased and manufacturing cost is increased.
Also, the automated optical inspection is sensitive to external vibration such that detection power is limited.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.